Diaphragm



May 8, 1923.

H. C. GAINS DIAPHRAGM.

Filed Nov, 5 1920 Patented May 8, 1923.

UNITED STATES HAROLD CECIL GAINS, OF LONDON, ENGLAND.

DIAPHRAGM.

Application flled November 5, 1920. Serial No. 422,047.

To allwhomit may concern:

Be it known that I, HAROLD CECIL GAINS, a subject of the King of Great Britain and Ireland, residin at 99 Highbury Quadrant, London, N. 5, England, have invented certain new and useful Improvements in a Diaphragm (for which I have filed application for patent in Great Britain, #17,147, July 9, 1919) and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to the sound box or reproducer for gramophones, phonographs and the like, and has for its object so to construct and mount an article of the class in question that the reproduction of the sound is superior to that obtained from sound boxes as at present constructed.

The invention relates both to the mounting and to the general construction of the sound box, and to the diaphragm for use therewith.

According to my invention, for attaching the sound box to the sound conduit, so that the box can be readily interchanged for another and so that the angular position of the needle can easily be varied or adjusted to suit requirements, I provide a flange near the end of the sound conduit, and I form a recess at the back of the sound box. The before mentioned flange is inserted into the recess with a resilient washer on each side, and a screw cap or its equivalent is provided screwing into or on to the back of the sound box, so that the flange can be clamped between the two resilient washers, after adjustment.

The foregoing construction is of particular advantage when used in connection with sound boxes of the known type in which the shell or body is made in two portions, the rear portion being provided with a recess for the reception of two gaskets between which the diaphragm is gripped, and having a ring carrying the stylus bar screwing into or on to the front of the shell to compress the gaskets and to cause the diaphragm to be held with the correct amount of tension as with this construction when the front of the sound box is rotated to alter the tension it may bring the needle into an unsuitable angular position for playing, and the position of the needle can then be adjusted to the most favourab e angle for playing by loosening the connection at the back, adjusting the position of the needle as required and then again tightening up the connection at the back.

The method of attachment is however also of general application since it affords an excellent insulating joint between the sound box and the sound conduit, preventing the transmission of undesirable vibrations.

In sound boxes of the type already mentioned, where a screw threaded ring carrying the stylus bar is provided, I find in practice that there is a tendency for the ring to turn somewhat when not required, thus varying the tension of the diaphragm, and to 0bviate this drawback, I rovide a set screw or the like passing throug the rin and screwing against the shell or equivai ent part, in order to lock the ring from movement, when not required.

The stylus bar in the sound box constructed according to my invention is pivoted between two pointe screws passing through lugs formed on the adjustable ring, and lock- 1ng screws are further provided for holding the before mentioned pointed screws in the adjusted position.

The diaphragm is manufactured from circular discs of thin unglazed paper of various sizes cemented or glued together and covered with a suitable layer of hard varnish or cellulose dope.

And in order that my said invention may be more clearly understood, I will now proceed to describe the same with reference to the accompanying drawing, which shows a diagrammatic, substantially diametric section of a sound box of the type already mentioned provided with a screwed ring at the front carrying the stylus bar, the said sound box having my improvements adapted thereto.

It is however to be understood that the drawing is given merely as one example of the application of my improvements.

Fig. 1 is a sectional view of a sound box provided with a diaphragm constructed in accordance with my invention.

Fig. 2 is a detail sectional view of the diaphragm on an exaggerated scale.

Fig. 3 is a detail sectional view, also on an exaggerated scale, of the paper discs of which the diaphragm is made, and showing the same separated.

a is the diaphragm, which is supported between two rubber gaskets 6, held under slight compression between a flanged ring 0 and the back plate (2 of the shell of the sound box.

In-the case illustrated the attachment of the ring is effected by means of a screw thread cut on the outside of a flange or wall of the shell or back plate 03 engaging a corresponding screw thread provided on the inside of the ring 0', as shown clearly in the drawing.

When the ring has been screwed to the desired position, to obtain the requisite tension, the two parts are securely lockedby means of the blunt nosed screw as passing through the ring and bearing upon the flange of the back plate or shell.

On the outer face of the back plate d, at the middle, is cast a short tubular extension k, and this is provided with an internal screw thread.

0 is a flanged ring with a screw thread cut on the exterior. As an alternative, the screw thread might of course be provided on the exterior of the tubular extension and a corresponding screw thread on the interior of the cap or ring 6.

Z is a flange on the connectin tube or sound conduit g, and f are flat rubdoer rings.

The flange Z is inserted into the recess in the ring 6 with a rubber ring on each side and when the ring or cap is screwed home it clamps the sound box in position.

The sound box is completely insulated from the tone arm or sound conduit. More- .over, by loosening the ring 0 the sound box can be rotated, thus enabling the needle to be adjusted in any desired angular position, and in the case of a sound box fitted with the tensioning ring at the front for the diaphragm, as previously described, the attachment enables the position to be readjusted to suit the position of the ring. It also enables the sound box to be interchanged for another, when required with great facility and allows a sound box to be attached to conduits or tone arms varying considerably in diameter.

The stylus bar it is pivotally mounted between two pointed screws m passing through two lugs formed on the ring of the sound box above referred to. These pivot screws m are locked in the adjusted position by blunt nosed screws n passing through the before mentioned lugs and bearing upon the pivot screws.

The diaphragm is manufactured from a plurality of circular discs 2 of various sizes of thin tough unglazed paper absolutely free from wax or grease. These discs are ilunited by a refined glue or cement applied iot.

The precise number of discs necessary to build up an effective diaphragm depends on the size of the finished diaphragm required and the exact qualities of the paper used.

For a diaphragm of say 21} inches in diameter, a total of about 11 discs will be required. In the case of 11 discs they would be united together in the following sequence, the minimum amount of glue being used Two discs 2% inches diameter, one disc 2 inches diameter, 2 discs 1% inches diameter,

1 disc 2 inches diameter, 2 discs 1% inches diameter, one disc 2 inches diameter, and finally 2 discs 2% inches diameter.

When the process is completed, the whole is laid aside for a time to allow the surplus moisture to evaporate.

Subsequently the discs are gradually pressed out flat by means of a warm iron, using as little pressure as possible. They are then again laid aside to cool and afterwards again ironed, using some slight pressure and at a temperature of about 200 F. After some few minutes of this treatment, the diaphragm is allowed to cool under pressure. When cool and the glue has solidified and so rendered the whole stifl', the diaphragm is immediatel covered with a thin, even layer 3 of hard varnish or dope. consisting preferably of cellulose acetate and such as is used to coat the fabric of the planes of flying machines to render the same taut and waterproof.

The commodity sold and known as Dopon is suitable for this last process.

What I claim and desire to secure by Letters Patent of the United States of America is The method of making a aper diaphragm consisting in arranging a plurality of paper discs in superposed relation, uniting them by a heated adhesive, causing the surplus moisture to evaporate, heating and pressing the united discs, cooling the same, repressing at a temperature of about 200 F., cooling the same while under pressure, and finally coating the same with varnish.

In testimony whereof, I have hereunto subscribed my name.

HAROLD CECIL GAINS. 

